In orthopedic surgery, it is well known that the use of intrathecal morphine (ITM) leads to an improved quality of postoperative analgesia. Little is known how this improved analgesia affects the long-term course after surgery.
Patients were randomly assigned to receive either 0.1 mg (n=16) or 0.2 mg (n=16) morphine sulfate intrathecally or physiological saline (n=17) added to 3 mL 0.5% isobaric bupivacaine for spinal anesthesia. As a function of the quality of the short-term postoperative analgesia, the effect on recovery and quality of life was evaluated at various time points up to 26 weeks after surgery.
In both ITM groups, the additionally required postoperative systemic morphine dose was significantly reduced compared with the placebo group ( P=0.004). One week after operation, patients with ITM reported significantly less pain at rest ( P=0.01) compared to the placebo group. At discharge, in comparison with the 0.1 mg ITM and placebo group, the 0.2 mg ITM group showed a higher degree of impairment regarding pain, stiffness, and physical function of the respective joint ( P=0.02). Over the further follow-up period of 6 months after surgery, recovery and the quality of life did not differ significantly between the three study groups ( P>0.2).
Morphine (0.1 mg) as adjunct to 0.5% bupivacaine for spinal anesthesia is effective to produce a pronounced postoperative analgesia with a beneficial analgesic effect up to 1 week after surgery. With this study design, the different quality of postoperative analgesia had no effect on quality of life and recovery in patients over the 6-month follow-up period. In the medium term, ITM may induce hyperalgesic effects.